a can is fylled with jam and it weighs 400g. when the can is fylled half it weighs 250g. how much does the can weigh?

                                            can +      jam = 400

                                            can + 1/2jam = 250

                                            -----------------------

Subtract the columns:                      1/2jam = 150

Multiply by 2:                                       jam = 300

Since can + jam = 400 and jam = 300, can = 100

Fylled...?

Doth ye write from Shakespeare's time?